I wanted to add that I think this thread does have merit and should remain on this site. I think the vast majority of people on this forum would agree that cheating is a bad idea and it's very strongly not advisable to get involved with people who are cheating on others.... However, I think that it's extremely unwise to forbid the discussion of situations that have involved cheating.
Like it or not, there are a lot of people who have discovered that they were poly because of an affair, and realized that while their behavior was wrong and then made right of the situation. Should we be discounting their experience that brought them where they are today? I don't think so.
There are also a lot of people out there that have ended up in situations where they've been involved with someone else who happens to be cheating... whether it be because they didn't have the foresight to ask about the person's other relationships, or because the person didn't end up being honest with their first partner, or whatever. That's a hard situation to find yourself in and break yourself away from.
People make mistakes. People learn from mistakes, both from their own and the mistakes of others. It's extremely unwise to pretend that mistakes don't happen and suggest that discussing them has no place in the community.